1. Field of the Invention
The present invention relates to an image search apparatus and an image processing apparatus, and in particular to an image processing apparatus that performs image processing for selecting an image that is suitable for use in image processing from among a plurality of images.
2. Related Background Art
As a method of detecting an object using a security camera or the like, known is a method of performing background differential with a taken image that is momentarily input and a background image that is taken in advance in the same position and same posture as the taken image, and detecting an object by extracting a region containing a difference between the two. Nevertheless, if the lighting conditions (in particular, weather conditions and time of imaging if outdoors) are different at the time of taking the input image and at the time of taking the background image, the appearance of shadows will differ in the input image and the background image. Consequently, it is not possible to specify whether the region that was extracted with the background differential is a shadow or an object that newly appeared. Thus, in order to perform high-precision background differential, it is necessary to take background images in advance under various lighting conditions, search for a background image having the same lighting conditions as the input image among a plurality of background images taken under the various lighting conditions, and perform background differential with the input image and the background image having the same lighting conditions.
As a method of searching for an image among a plurality of search-target images, there is a method of searching for an image having the same characterizing portion as the input image based on the characterizing portion as a search key that is designated by an operator or designated automatically. The image search apparatus described in Japanese Patent Application Laid-Open No. 2004-21430 calculates the similarity of corresponding regions between the reference image and each of the plurality of search-target images, seeking a similarity level based on a characteristic amount of a certain region with high similarity, and extracting an image that is similar to the reference image among a plurality of search-target images based on that similarity level (Patent Literature 1: Japanese Patent Application Laid-Open No. 2004-21430, Patent Literature 2: Japanese Patent Application Laid-Open No. 2000-163576, Patent Literature 3: Japanese Patent Application Laid-Open No. H11-312248, Patent Literature 4: Japanese Patent Application Laid-Open No. H8-263522).
Meanwhile, conventionally known is an image processing apparatus for extracting a similar image among a plurality of images (for instance, refer to Japanese Patent Publication No. H7-107683). This image processing apparatus extracts a characteristic amount from an image that was input, and, with the extracted characteristic amount as the key, searches for an image having a characteristic amount that is similar to such key from an image database, and thereby automatically extracts an image that is similar to the image that was input (Japanese Patent Publication No. H7-107683).